Add methods for listening on multiple addresses

Add listen_tcp and listen_ssl which implement Twisted's reactor.listenTCP
and reactor.listenSSL for multiple addresses.

Signed-off-by: Silke Hofstra <silke@slxh.eu>

synapse/app/_base.py

@@ -25,7 +25,7 @@ except Exception:
 from daemonize import Daemonize
 from synapse.util import PreserveLoggingContext
 from synapse.util.rlimit import change_resource_limit
-from twisted.internet import reactor
+from twisted.internet import error, reactor
 
 
 def start_worker_reactor(appname, config):
@@ -120,3 +120,58 @@ def quit_with_error(error_string):
         sys.stderr.write(" %s\n" % (line.rstrip(),))
     sys.stderr.write("*" * line_length + '\n')
     sys.exit(1)
+
+
+def listen_tcp(logger, bind_addresses, port, factory, backlog=50):
+    """
+    Create a TCP socket for a port and several addresses
+    """
+    for address in bind_addresses:
+        try:
+            reactor.listenTCP(
+                port,
+                factory,
+                backlog,
+                address
+            )
+        except error.CannotListenError as e:
+            check_bind_error(logger, e, address, bind_addresses)
+
+
+def listen_ssl(logger, bind_addresses, port, factory, context_factory, backlog=50):
+    """
+    Create an SSL socket for a port and several addresses
+    """
+    for address in bind_addresses:
+        try:
+            reactor.listenSSL(
+                port,
+                factory,
+                context_factory,
+                backlog,
+                address
+            )
+        except error.CannotListenError as e:
+            check_bind_error(logger, e, address, bind_addresses)
+
+
+def check_bind_error(logger, e, address, bind_addresses):
+    """
+    This method checks an exception occurred while binding on 0.0.0.0.
+    If :: is specified in the bind addresses a warning is shown.
+    The exception is still raised otherwise.
+
+    Binding on both 0.0.0.0 and :: causes an exception on Linux and macOS
+    because :: binds on both IPv4 and IPv6 (as per RFC 3493).
+    When binding on 0.0.0.0 after :: this can safely be ignored.
+
+    Args:
+        logger (Logger): Logger used to log the warning.
+        e (Exception): Exception that was caught.
+        address (str): Address on which binding was attempted.
+        bind_addresses (list): Addresses on which the service listens.
+    """
+    if address == '0.0.0.0' and '::' in bind_addresses:
+        logger.warn('Failed to listen on 0.0.0.0, continuing because listening on [::]')
+    else:
+        raise e

synapse/app/homeserver.py

@@ -131,9 +131,9 @@ class SynapseHomeServer(HomeServer):
         root_resource = create_resource_tree(resources, root_resource)
 
         if tls:
-            for address in bind_addresses:
-                try:
-                    reactor.listenSSL(
+            _base.listen_ssl(
+                logger,
+                bind_addresses,
                 port,
                 SynapseSite(
                     "synapse.access.https.%s" % (site_tag,),
@@ -142,26 +142,20 @@ class SynapseHomeServer(HomeServer):
                     root_resource,
                 ),
                 self.tls_server_context_factory,
-                        interface=address
             )
-                except error.CannotListenError as e:
-                    check_bind_error(e, address, bind_addresses)
 
         else:
-            for address in bind_addresses:
-                try:
-                    reactor.listenTCP(
+            _base.listen_tcp(
+                logger,
+                bind_addresses,
                 port,
                 SynapseSite(
                     "synapse.access.http.%s" % (site_tag,),
                     site_tag,
                     listener_config,
                     root_resource,
-                        ),
-                        interface=address
                 )
-                except error.CannotListenError as e:
-                    check_bind_error(e, address, bind_addresses)
+            )
         logger.info("Synapse now listening on port %d", port)
 
     def _configure_named_resource(self, name, compress=False):
@@ -239,19 +233,16 @@ class SynapseHomeServer(HomeServer):
             elif listener["type"] == "manhole":
                 bind_addresses = listener["bind_addresses"]
 
-                for address in bind_addresses:
-                    try:
-                        reactor.listenTCP(
+                _base.listen_tcp(
+                    logger,
+                    bind_addresses,
                     listener["port"],
                     manhole(
                         username="matrix",
                         password="rabbithole",
                         globals={"hs": self},
-                            ),
-                            interface=address
                     )
-                    except error.CannotListenError as e:
-                        check_bind_error(e, address, bind_addresses)
+                )
             elif listener["type"] == "replication":
                 bind_addresses = listener["bind_addresses"]
                 for address in bind_addresses:
@@ -264,7 +255,7 @@ class SynapseHomeServer(HomeServer):
                             "before", "shutdown", server_listener.stopListening,
                         )
                     except error.CannotListenError as e:
-                        check_bind_error(e, address, bind_addresses)
+                        _base.check_bind_error(logger, e, address, bind_addresses)
             else:
                 logger.warn("Unrecognized listener type: %s", listener["type"])
 
@@ -298,13 +289,6 @@ class SynapseHomeServer(HomeServer):
         return db_conn
 
 
-def check_bind_error(e, address, bind_addresses):
-    if address == '0.0.0.0' and '::' in bind_addresses:
-        logger.warn('Failed to listen on 0.0.0.0, continuing because listening on [::]')
-    else:
-        raise e
-
-
 def setup(config_options):
     """
     Args: